In wind turbine blades, cross-flows of airflow sometimes propagate along the longitudinal length of the wind turbine blade, from the root end of the blade. Such cross-flows act to negatively impact on blade performance, in particular by contributing to airflow detachment from the surface of the blade, thereby affecting blade lift.
It is known to provide a barrier or stall fence which extends across the surface of a wind turbine blade, transverse to the longitudinal axis, to prevent the formation of such cross-flows. An example of such a wind turbine blade can be seen in U.S. Pat. No. 7,585,157.
While this system prevents the cross-flows from propagating along the blade length by providing a barrier between adjacent sections of the blade, during rotation of the wind turbine blades the centrifugal forces generated during rotation act to push airflow along the length of the blade towards the tip end. This results in the formation of low-pressure areas in the wake of the stall fences towards the trailing edge of the blades, resulting in flow separation and resultant reduction in blade performance.
It is an object of the invention to provide a wind turbine blade having a projecting member which provides improved performance over existing stall fence systems.